The present invention relates to apparatus for measuring usage of a commodity. More particularly, the invention relates to an electronic electric meter for measuring consumption of electricity and communicating that usage data and other power information to a utility over a two-way wireless local area network (LAN) to a remotely located gateway node that transmits the data over a two-way fixed common carrier wide area network (WAN), or communicating that data directly to the utility, over a commercially available two-way data communication network.
Commodity usage is conventionally determined by utility companies using meters that monitor subscriber consumption. The utility service provider typically determines the subscriber's consumption by sending a service person to each meter location to manually record the information displayed on the meter dial. The manual reading is then entered into a computer which processes the information and outputs a billing statement for the subscriber. However, it is often difficult for the service person to access the meter for reading, inspection and maintenance. When access to a meter is not possible, billings are made on the basis of estimated readings. These estimated billings often lead to customer complaints.
Currently available electric meters such as watt-hour meters work well for their intended purpose, but they must be manually read. This makes it difficult to cost effectively measure electricity usage for each user to promote fair billing and encourage conservation. Manual reading of electric meter is highly labor intensive, inefficient and very expensive. Therefore, there has been a strong interest on the part of utility companies to take advantage of modern technology to reduce operating costs and increase efficiency by eliminating the necessity for manual readings.
Many attempts have been made in recent years to develop an automatic meter reading system for electric meters which avoid the high costs of manual meter reading. However, most of these prior art systems have achieved little success. For automatic or remote meter reading, a transducer unit must be used with the meters to detect the output of such meters and transmit that information back to the utility.
Various types of devices have been attached to utility meters in an effort to simplify meter reading. These devices were developed to transfer commodity usage data over a communication link to a centrally located service center or utility. These communication links included telephone lines, power lines, or a radio frequency (RF) link.
The use of existing telephone lines and power lines to communicate commodity usage data to a utility have encountered significant technical difficulties. In a telephone line system, the meter data may interfere with the subscriber's normal phone line operation, and would require cooperation between the telephone company and the utility company for shared use of the telephone lines. A telephone line communication link would also require a hard wire connection between the meter and the main telephone line, increasing installation costs. The use of a power line carrier (PLC) communication link over existing power lines would again require a hard wire connection between the meter and the main power line. Another disadvantage of the PLC system is the possibility of losing data from interference on the power line.
Meters have been developed which can be read remotely. Such meters are configured as transducers and include a radio transmitter for transmitting data to the utility. These prior art systems required the meter to be polled on a regular basis by a data interrogator. The data interrogator may be mounted to a mobile unit traveling around the neighborhood, incorporated within a portable hand-held unit carried by a service person, or mounted at a centrally located site. When the meter is interrogated by a RF signal from the data interrogator, the meter responds by transmitting a signal encoded with the meter reading and any other information requested. The meter does not initiate the communication.
However, such prior art systems have disadvantages. The first disadvantage is that the device mounted to the meter generally has a small transceiver having a very low power output and thus a very short range. This would require that the interrogation unit be in close proximity to the meters. Another disadvantage is that the device attached to the meter must be polled on a regular basis by the data interrogator. The device attached to the meter is not able to initiate a communication. The mobile and hand-held data interrogators are of limited value since it is still necessary for utility service personnel to travel around neighborhoods and businesses to remotely read the meters. It only avoids the necessity of entering a residence or other building to read the meters. The systems utilizing a data interrogator at fixed locations still have the disadvantages of low power output from the devices attached to the meters, and requiring polling by the data interrogator to initiate communication.
Therefore, although automatic meter reading systems are known in the prior art, the currently available automatic meter reading systems suffer from several disadvantages, such as low operating range and communication reliability. Thus, it would be desirable to provide an electronic electric meter to retrofit into existing meter sockets or for new installations that enables cost effective measurement of electricity usage by a consumer. It would also be desirable to have an electric meter that is capable of providing automatic networked meter reading.